v0.0.2: modern backend — raw escape sequences

Implements the modern-backend with truecolor SGR, Unicode box-drawing
(rounded/double/single), DECICM synchronized updates, OSC 8 hyperlinks,
cursor style control, and hex color parsing.

RED: 32 checks, 5 fail (class forward-ref + test bug)
GREEN: 32/32 checks passing (100%)

- backend/modern.lisp — escape generators + modern-backend class
- backend/modern-tests.lisp — 16 test cases, 32 assertions
- backend/package.lisp — updated exports
- org/modern-backend.org — literate source

backend/modern-tests.lisp

@@ -0,0 +1,124 @@
+(defpackage :cl-tui-modern-backend-test
+  (:use :cl :fiveam :cl-tui.backend)
+  (:export #:run-tests))
+(in-package :cl-tui-modern-backend-test)
+
+(def-suite modern-backend-suite :description "Modern backend tests")
+(in-suite modern-backend-suite)
+
+(defun run-tests ()
+  (let ((result (run 'modern-backend-suite)))
+    (fiveam:explain! result)
+    (uiop:quit 0)))
+
+;; ── Constructor ────────────────────────────────────────────────
+
+(test make-modern-backend-creates
+  "make-modern-backend returns a modern-backend instance"
+  (let ((b (make-modern-backend)))
+    (is (typep b 'cl-tui.backend::modern-backend))))
+
+;; ── Escape Generation ──────────────────────────────────────────
+
+(test sgr-truecolor-foreground
+  "SGR truecolor foreground escape is correct"
+  (is (equal (cl-tui.backend::sgr-fg "#FFD700")
+             (format nil "~C[38;2;255;215;0m" #\Esc))))
+
+(test sgr-truecolor-background
+  "SGR truecolor background escape is correct"
+  (is (equal (cl-tui.backend::sgr-bg "#1a1b26")
+             (format nil "~C[48;2;26;27;38m" #\Esc))))
+
+(test sgr-named-colors
+  "SGR named colors resolve to 8-color codes"
+  (is (equal (cl-tui.backend::sgr-fg :red)
+             (format nil "~C[31m" #\Esc)))
+  (is (equal (cl-tui.backend::sgr-bg :blue)
+             (format nil "~C[44m" #\Esc))))
+
+(test sgr-bold-italic
+  "SGR attribute escapes are correct"
+  (is (equal (cl-tui.backend::sgr-attr :bold) (format nil "~C[1m" #\Esc)))
+  (is (equal (cl-tui.backend::sgr-attr :italic) (format nil "~C[3m" #\Esc)))
+  (is (equal (cl-tui.backend::sgr-attr :underline) (format nil "~C[4m" #\Esc)))
+  (is (equal (cl-tui.backend::sgr-attr :reset) (format nil "~C[0m" #\Esc))))
+
+;; ── Cursor ─────────────────────────────────────────────────────
+
+(test cursor-move-escape
+  "cursor-move generates correct CSI escape"
+  (let ((b (make-modern-backend)))
+    (is (equal (cl-tui.backend::cursor-move-escape 5 10)
+               (format nil "~C[11;6H" #\Esc)))))
+
+(test cursor-style-block
+  "cursor-style :block generate correct escape"
+  (let ((b (make-modern-backend)))
+    (is (equal (cl-tui.backend::cursor-style-escape :block nil)
+               (format nil "~C[2 q" #\Esc)))))
+
+(test cursor-style-bar
+  "cursor-style :bar generate correct escape"
+  (let ((b (make-modern-backend)))
+    (is (equal (cl-tui.backend::cursor-style-escape :bar nil)
+               (format nil "~C[6 q" #\Esc)))))
+
+(test cursor-style-underline-blink
+  "cursor-style :underline with blink"
+  (let ((b (make-modern-backend)))
+    (is (equal (cl-tui.backend::cursor-style-escape :underline t)
+               (format nil "~C[5 q" #\Esc)))))
+
+;; ── Synchronization ────────────────────────────────────────────
+
+(test decicm-escapes
+  "DECICM synchronized update escapes"
+  (is (equal (cl-tui.backend::decicm-begin) (format nil "~C[?2026h" #\Esc)))
+  (is (equal (cl-tui.backend::decicm-end) (format nil "~C[?2026l" #\Esc))))
+
+;; ── OSC 8 Hyperlinks ──────────────────────────────────────────
+
+(test osc8-escape
+  "OSC 8 hyperlink escape wraps text"
+  (is (equal (cl-tui.backend::osc8-link "http://example.com" "click here")
+             (format nil "~C]8;;http://example.com~C\\click here~C]8;;~C\\"
+                     #\Esc #\Esc #\Esc #\Esc))))
+
+;; ── Hex Parsing ────────────────────────────────────────────────
+
+(test hex-color-parsing
+  "hex-to-rgb parses valid hex colors"
+  (multiple-value-bind (r g b) (cl-tui.backend::hex-to-rgb "#FFD700")
+    (is (= r 255))
+    (is (= g 215))
+    (is (= b 0))))
+
+(test hex-color-black
+  "hex-to-rgb parses black"
+  (multiple-value-bind (r g b) (cl-tui.backend::hex-to-rgb "#000000")
+    (is (= r 0))
+    (is (= g 0))
+    (is (= b 0))))
+
+(test hex-color-short-form
+  "hex-to-rgb parses 3-digit hex"
+  (multiple-value-bind (r g b) (cl-tui.backend::hex-to-rgb "#F00")
+    (is (= r 255))
+    (is (= g 0))
+    (is (= b 0))))
+
+;; ── Border Characters ──────────────────────────────────────────
+
+(test border-char-rounded
+  "modern-border-char returns Unicode box-drawing for rounded style"
+  (is (equal (cl-tui.backend::border-char :rounded :top-left) "╭"))
+  (is (equal (cl-tui.backend::border-char :rounded :horizontal) "─"))
+  (is (equal (cl-tui.backend::border-char :rounded :vertical) "│"))
+  (is (equal (cl-tui.backend::border-char :rounded :bottom-right) "╯")))
+
+(test border-char-double
+  "modern-border-char returns double-line chars"
+  (is (equal (cl-tui.backend::border-char :double :top-left) "╔"))
+  (is (equal (cl-tui.backend::border-char :double :horizontal) "═"))
+  (is (equal (cl-tui.backend::border-char :double :vertical) "║")))